Toxicity of trichothecenes, moniliformin, zearalenone/ol, griseofulvin, patulin, PR toxin and rubratoxin B on protozoan tetrahymena pyriformis.

The inhibitory effects of some fungal products from Fusarium, Trichothecium, Myrothecium and Penicillium were investigated on the protozoan Tetrahymena pyriformis. The dose of mycotoxin which decreased the protozoa growth by 50% in 24 h was defined as inhibitory dose 50 (ID50). The order of toxicity according to the ID50 values were: T-2 toxin greater than trichothecin greater than 4, 15-diacetylverrucarol greater than patulin greater than trichothecolone greater than verrucarol greater than zearalenone greater than PR toxin greater than 3 alpha-acetyldiacetoxyscirpenol greater than zearalenol greater than griseofulvin greater than acetyl T-2 greater than iso T-2 greater than T-2 triol greater than scirpentriol greater than rubratoxin B greater than T-2 tetraol greater than moniliformin. In analogous pairs of trichothecenes their toxicities depended upon the substituents at certain positions of the molecules. Thus, the order of toxicity by the substituents was: at C3 position, H greater than OH greater than OAc [e.g., verrucarol (H at C3) greater than scirpentriol (OH at C3); T-2 toxin (OH at C3) greater than acetyl T-2 (OAc at C3); 4,15-diacetylverrucarol (H at C3) greater than 3 alpha-acetyldiacetoxyscirpenol (OAc at C3)]; at C4 position, OAc greater than OH, and isocrotonyl greater than OH [e.g., acetyl T-2 (OAc at C4) greater than iso T-2 (OH at C4); trichothecin (isocrotonoyl at C4) greater than trichothecolone (OH at C4)]; at C8 position, H greater than isovaleryl greater than OH [e.g., 3 alpha-acetyldiacetoxyscirpenol (H at C8) greater than acetyl T-2 (isovaleryl at C8); T-2 triol isovaleryl at C8) greater than T-2 tetraol (OH at C8); scirpentriol (H at C8) greater than T-2 tetraol (OH at C8)]. Among trichothecenes (without ester groups) with H and OH substituents, the toxicity was inversely related to the number of OH groups in the molecule: verrucarol (2 OHs) greater than scirpentriol (3 OHs) greater than T-2 tetraol (4 OHs). Zearalenone was about 3 times more toxic than its analogue zearalenol. The Tetrahymena cultures exposed 1 d to mycotoxins had protozoa counts/microliters inversely related to doses, and the % transmittance and pH values were directly related to doses.